Described herein are processes for the preparation of bio-based fiber gums involving:
(a) mixing agricultural materials with a heated alkaline solution at temperatures in the range of about 75° to about 150° C. (and preferably in the range of about 85° to about 90° C.) to form a slurry;
(b) separating out the insoluble components from said slurry to yield a solution having a pH of about 9 to about 14 (and preferably in the range of about 10 to about 12) wherein said solution contains about 0.1 to about 10 wt % solids wherein said solids are alkaline soluble fractions;
and one of the following:
(c) evaporating said solution to about 16 to about 23 wt % solids and drying to a powder;
(d) adjusting the pH of said solution to a pH of about 2 to about 12 (and preferably to a pH of about 4 to 10 and more preferably to a pH of about 4 to about 7), evaporating said solution to about 16 to about 23 wt % solids and drying to a powder;
(e) evaporating said solution to about 16 to about 23 wt % solids, adjusting the pH of said solution to a pH of about 2 to about 12 (preferably to a pH of about 4 to 10 and more preferably to a pH of about 4 to about 7), and drying to a powder;
(f) evaporating said solution to about 16 to about 23 wt % solids and precipitating out said soluble components with about two to about five volumes of organic solvent (e.g., ethanol, isopropanol) to form a precipitate and a supernatant, and separately drying said precipitate and said supernatant;
(g) evaporating said solution to about 16 to about 23 wt % solids, adjusting the pH of said solution to a pH of about 2 to about 12 (preferably to a pH of about 4 to 10 and more preferably to a pH1 of about 4 to about 7), and precipitating out said soluble components with one to five volumes (preferably 2 volumes) of organic solvent (e.g., ethanol, isopropanol) to form a precipitate and a supernatant, and separately drying said precipitate and said supernatant;
(h) adjusting the pH of said solution to a pH of about 2 to about 12 (preferably to a pH of about 4 to 10 and more preferably to a pH of about 4 to about 7), evaporating said solution to about 16 to about 23 wt % solids and precipitating out said soluble components with about one to five volumes (preferably about 2 volumes) of organic solvent (e.g., ethanol, isopropanol) to form a precipitate and a supernatant, and separately drying said precipitate and said supernatant; or
(i) adjusting the pH of said solution to a pH of about 2 to about 5 (preferably to about 3.5 to about 4.5) to precipitate Hemicellulose A and the remaining solution is treated with about 2 volumes of organic solvent (e.g., ethanol, isopropanol) to form a precipitate and a supernatant, and separately drying said precipitate and said supernatant; and
optionally the solution is pretreated with at least one of the following:
(1) de-salting said solution and the de-salted solution becomes the solution;
(2) processing the solution through at least one nano-filtration membrane or ultra-filtration membrane or diafiltration membrane and the permeate becomes the solution; or
(3) processing the solution through at least one nano-filtration membrane or ultra-filtration membrane or diafiltration membrane and the retentate becomes the solution.
Also described are products produced by these processes and some of their uses.
When lignocellulosic agricultural residues (e.g., corn stover, wheat straw, rice straw, etc.), agricultural processing byproducts (e.g., corn bran, corn fiber, oat bran, rice hull, sugarcane bagasse, etc.), and energy crops (e.g., miscanthus, switch grass, etc.) are extracted with alkaline solutions to produce cellulose-enriched fractions for food and biofuel applications, there is a waste stream from the process that must undergo expensive waste treatment before it can be disposed. Simultaneously, there is currently a demand for low cost, biobased products that can substitute for petroleum-derived and/or imported oil-in-water and water-in-oil emulsifiers, adhesives, binding agents, useful components of oil-well drilling- and hydraulic fracturing-fluids, viscosifiers, antioxidants, soluble dietary fibers, and serum cholesterol reducing agents. Surprisingly, we have found that the waste stream from the lignocellulosic product processing noted above, can be processed by evaporating, drying, membrane filtration, solvent precipitation and/or other methods described herein to yield novel compositions that can function as substitutes for the petroleum-derived and/or imported products noted above. This finding thus allows the conversion of a waste material with negative value to a value added-product with many applications described herein.